Cartridge and printer system for using roll print media

For use with a portable printer having a housing with a print media ingress in its lower rear wall and a print media egress in its top wall, a print media cartridge comprising:

• (a) a cartridge housing including:
• (i) an elongated member of generally U-shaped cross-section having a top wall portion and a bottom wall portion with a planar bottom surface and (ii) two end wall portions closing the ends of said elongated member;
• (b) a cartridge door of size and shape corresponding to the open side of said elongated member;
• (c) means for hingedly coupling said cartridge door to the lip of said bottom wall portion of said elongated member;
• (d) means for latching said cartridge door in a closed position to said cartridge housing;
• and
• (e) a roll of print media supported within said cartridge housing in an orientation such that the roll ends face respective end wall portions and that its lead edge unwinds adjacent said bottom wall portion;
• said cartridge door being a planar element constructed to rest, in an open condition, on a flat surface coplanar with said bottom wall portion and be held under the printer housing so that the printer weight retains an operative cartridge position vis-a-vis said printer.